--- a/mercurial/cmdutil.py	Wed Aug 02 19:13:56 2017 +0200
+++ b/mercurial/cmdutil.py	Wed Aug 02 19:20:59 2017 +0200
@@ -1913,7 +1913,7 @@
     To be used by debug function."""
     if index is not None:
         fm.write('index', '%i ', index)
-    fm.write('precnode', '%s ', hex(marker.precnode()))
+    fm.write('precnode', '%s ', hex(marker.prednode()))
     succs = marker.succnodes()
     fm.condwrite(succs, 'succnodes', '%s ',
                  fm.formatlist(map(hex, succs), name='node'))